Safety device for elevators



April 17, 1934. R p. JACKSQN 1,955,333

SAFETY DEVICE FOR ELEVATORS Filed June 16, 1930 z 46 firm INVENTOR Ray F. Jae/(50a ATTORNEY Patented Apr. 17, 1934 7 SAFETY DEVICE FOR ELEVATORS Ray P. Jackson, Wilkinsburg, 1a., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application June 16, 1930, Serial No. 461,279

3 Claims.

My invention relates to safety devices for elevators and more particularly to means for actuating such safety devices. 7

One object of my invention is to provide a safety mechanism for elevators which shall be responsive to a predetermined rate of downward acceleration of the car, and which may be manually operated at the will of the operator, for stopping the car when it falls or starts to run away.

Another object is to provide a safety mechanism for stopping an elevator car which will respond to a predetermined downward acceleration of the car, but which will not be affected by any upward acceleration of the car.

A further object of my invention is to provide a safety mechanism for elevators that may be readily adjusted to approximate different ccnditions of service in order that it may be tested with case under a variety of conditions.

It is also an object of my invention to provide a safety mechanism for elevators which shall be responsive to a predetermined speed, as Well as to a predetermined rate of acceleration.

Other objects of my invention will, in part, be obvious and will, in part, appear hereinafter.

In the accompanying drawing, which illustrates a preferred embodiment of my invention;

The single figure is a diagrammatic representation of an elevator embodying means for actuating a safety device constructed in accordance with my invention.

In order to provide for the safe operation of elevators, each car is usually supplied with a safety car-stopping device comprising two pairs of gripping jaws which are disposed underneath the car in position to engage the guide rails at the sides of the car, when the car falls, for the purpose of bringing it to a stop.

In some cases, the gripping jaws are applied to the guide rails by means of stored-up power, such as may be obtained from compressed springs in conjunction with operating wedges. In other cases, the gripping jaws are applied to the guide rails by means of wedge-shape expanding members which are projected by screw action of a safety cable drum.

In either case, the release of the stored-up power or the operation or" the rotatable cylinder is usually effected by a safety rope which is firmly secured to a governor rope. The governor rope is releasably attached to the car, from which point it runs to an overhead sheave mounted in the upper part of the hatchway and thence to and around a weighted sheave located at the lowor end of the hatchway and back to the car. The governor rope normally moves with the car and rotates the upper and lower sheaves. to the overhead sheave is a centrifugal governor which, when rotated above a predetermined speed, releases a locking device which operates immediately to firmly grip the governor rope and arrest its movement, if the car is descending. When the movement of the governor rope is arrested, it is automatically released from the car by the releasable attaching means. Thereupon, the continued downward movement of the car causes the governor rope to pull on the safety rope to thereby release the safety device and apply the gripping jaws to the guide rails with increasing pressure, until the car is brought to a stop.

Inasmuch as the operation of the safety jaws is initiated and controlled by a centrifugal governor set to operate at some maximum speed above the usual speed at which the car runs, it may properly be called a'speed-controlled system. Such speed-controlled systems have been in use for many years, but, since their introduction, the normal running speeds of many elevator cars have been materially increased, largely because of the increased heights of buildings and also because of the necessity for increasing the work performed by the individual elevators. When the speed of a car is increased, it follows that the maximum speed at which the centrifugal governor will become effective to stop the car must also be correspondingly increased.

In order to provide a more effective elevator safety device operable in response to either an increase in speed or to the rate of acceleration of the car, I have provided a novel governing device which is readily adjustable for stopping the car at different predetermined speeds and rates of acceleration.

As illustrative of the present invention, I have shown inthe drawing an elevator car 1 supported by a hoisting cable 2 between a pair of guide rails 3 and 4. Secured to the bottom of the car 1, is the usual safety-grip device 5 which comprises two pairs of jaws 6 and 7 disposed to grip the guide rails 3 and 4 and stop the car when the car starts to fall or run away downwardly. A pair of operating screw rods 8 and 9 connect the gripping jaws 6 and '7 to a safety cable drum 10 which, when rotated, causes the jaws to grip the guide rails. The means for rotating the safety cable drum 10 comprises a safety rope 11, one end of which is secured to, and wound around, the drum l0 and the other end of which passes over a pair of sheaves 12 and 13 and is firmly Attached fastened to a governor rope 14, such as is usually provided in elevator installations.

The governor rope 14 is releasably attached to the car 1 by means of any suitable yielding connection 15, and passes over a sheave 16 connected to a centrifugal governor 17, mounted at the top of the hatchway, for the purpose of rotating the governor in accordance with the speed of the up and the down movements of the car.

The governor 17 is provided with a base 18 upon which a standard 19 is secured by suitable means, such as a plurality of bolts 20. Mounted in a suitable bearing 22 in the standard 19, is a rotatable shaft 21. The sheave 16, operated by the governor rope 14, is mounted on one end of the shaft 21, while a gear wheel 23 is mounted on its other end in position to mesh with a cooperating gear wheel 24 mounted on the lower end of a vertical member or tubular shaft or operating sleeve 25 on the lift rod 26. The sleeve 25 is rotatably mounted in suitable apertures 2'7 pro vided in a pair of arms 28 which project laterally from the standard 19. The upper end of the sleeve 25 is provided with a threaded portion 29 and rotatably supports a frame 30. The frame 30 is provided with a threaded aperture 30 which engages the threaded portion 29 of the sleeve 25.

A collar 32 rests on the upper arm 28 and constitutes a base on which the frame 30 may rotate. A pair of bell-crank levers 31 are pivotally mounted on the frame 30, at the outer periphery thereof, by means of pins 31. The outer arms 33 of the levers 31 carry a pair of weights or balls 34, and the inner arms 35 are preferably formed as arcuate members which engage a collar 36 rigidly mounted on the upper end of the rod 26.

The weights 34 move outwardly under the action of centrifugal force, when the speed of the elevator exceeds a predetermined limit. The outward movement of the weights 34 causes the inner arms 35 to move upwardly, thereby raising the collar 36 and the rod 26. A collar 37 is mounted on the lower end of the rod 26 and operates to raise a lever 38 when the rod 26 is raised by the action of the weights 34.

A pivotally mounted cam lever 39 is engaged by the right-hand end of the lever 38 in such manner that, when the lever 38 is raised by the action of the governor, the cam lever 39 will be raised, thereby causing its gripping jaw 40 to wedge the governor rope 14 against a cooperating jaw 41 and lock the rope against further movement. When the car 1 moves at a speed in excess of a predetermined maximum speed, the rope 14 will cause the governor to operate to lift the rod 26 and lever 38, whereby to actuate the gripping jaw 40 and lock the governor rope 14 against further movement. When the governor rope 14 is locked by the jaw 40, it will be pulled free from its yielding connection on the car and unwind the safety rope 11 from the safety cable drum 10, thereby applying the gripping jaws 6 and '7 to the guide rails 3 and 4 to stop the car.

Operation of the safety device will be effected also, when the rate of acceleration of the car exceeds a predetermined value in the downward direction of movement of the car. Any excessive acceleration of the car downwardly will cause a corresponding acceleration of the sleeve 25 which carries the frame 30.

The mass of the frame 30 and that of the balls 34, bearing downwardly, and the action of the engaging threaded portions 29 and 30 on the sleeve 25 and frame 30 respectively cause the latter to normally rotate with the sleeve 25 during a uniform acceleration of the shaft. However, if the acceleration of the car, in a downward direction, exceeds a predetermined value, the inertia of the frame offers a resisting force which over comes the unitary action between the threaded portions 29 and 30'.

Since the frame 30 is freely rotatable on the threaded portion of the sleeve, the former will move upwardly when the acceleration of the sleeve is so great that the resistance of the screw action between the threaded portions 29 and 30 can no longer overcome the inertia of the frame 30. Up ward movement of the frame 30 permits the bellcrank levers 31 to move upwardly to make contact with, and raise, the collar 36 on the rod 26, thereby causing the operation of the safety device as described above, on the occurrence of an excessive speed of the car. It will be understood that operation of the safety device at different predetermined rates of speed may be obtained by changing the size of the weights 34 carried by the frame 30.

i In order that the governor may be readily ad" justed to operate the safety device at different rates of acceleration, the inertia frame 30 is provided with extended portions 43 and 44.

Weights 45 are adjustably mounted on the portions 43 and 44 by means of shanks 46 formed integral therewith and adapted to be received by apertures 47 in the extended portions. If it is desired to change the rate of acceleration necessary to trip the safety device, the weights 45 may be moved toward or away from the axis of the sleeve 25, thereby changing the inertia in the frame 30, which, in turn, correspondingly varies the resistance to the action of the threaded portions 29 and 30', so that the safety device will be tripped, at varying rates of acceleration, with a minimum of effort. This method also provides an eificient means for testing the elevator safety device.

Any upward acceleration of the car has no effect on the governing device shown in the drawing, since the acceleration will only cause the frame 30 to seat on the associated collar owing to the direction of the threads on the shaft with respect to the direction of travel of the sleeve.

Various changes may be made in the specific embodiments of the present invention shown in the drawing, without departing from the spirit thereof, or from the scope of the appended claims.

I claim as my invention:

1. In combination an elevator car, a safety braking device carried thereby, and a governor comprising means operably responsive to a pre determined speed, means responsive to a predetermined rate of acceleration of the elevator car and means actuated by either of said means for applying said safety braking device to stop the car.

2. The combination with an elevator car and a safety braking device carried thereby, of a governor comprising means operably responsive to either a predetermined speed or a predctermined rate of downward acceleration of the car for actuating the safety braking device.

3. In combination an elevator car, a safety braking device carried thereby, a governor operably responsive to either a predetermined speed or a predetermined rate of downward acceleration of the car for causing the safety device to stop it, and means for adjusting said governor to render it responsive to varying rates of acceleration.

RAY P. JACKSON. 

